1. Evidence of an increased risk of lung cancer associated with cigarette smoking was sought by Doll and Hill. In one study, 649 lung cancer cases were matched by age, and gender to 649 controls; 647 of the cases and 622 of the control had a history of smoking cigarettes.
a. Name the type of study.
b. Create the appropriate 2X2 table for the study.
Lung Cancer Controls
Smokers 647 622
Nonsmokers 2 27
Total 649 649
c. Calculate the appropriate measure of association for the study.
d. Interpret the results.
A Case control study
34.5
a. The type of study conducted by Doll and Hill is a case-control study.
b. The appropriate 2x2 table for the study is as follows:
| Lung Cancer | Controls | Total
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Smokers | 647 | 622 | 1269
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Non-smokers | 2 | 27 | 29
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Total | 649 | 649 | 1298
c. To calculate the measure of association for the study, we will use the odds ratio (OR). The formula to calculate the odds ratio is:
OR = (a*d) / (b*c)
where:
a = number of exposed cases (smokers with lung cancer)
b = number of exposed controls (smokers without lung cancer)
c = number of unexposed cases (non-smokers with lung cancer)
d = number of unexposed controls (non-smokers without lung cancer)
In this case, we have:
a = 647
b = 622
c = 2
d = 27
Using these values in the formula, we can calculate the odds ratio:
OR = (647 * 27) / (622 * 2)
d. To interpret the results of the study, we need to compare the odds ratio calculated to 1. If the odds ratio is greater than 1, it indicates an increased risk of lung cancer associated with smoking. If the odds ratio is less than 1, it suggests a decreased risk. In this case, you can calculate the odds ratio from part c and compare it to 1. If the odds ratio is significantly higher than 1, it suggests a strong association between smoking and lung cancer.